1. Field of the Invention
The present invention relates in general to an apparatus and method of adjusting a horizontal position adjustment apparatus for a video display appliance, and more particularly, to an apparatus and method of adjusting a horizontal position that detects an overlap signal of a horizontal flyback pulse signal and a video signal, and adjusts the horizontal position using the overlap signal.
2. Description of the Prior Art
Video display appliances such as monitors include a horizontal position adjustment circuit in order to place the display image in the center of the screen.
Such conventional apparatuses and methods of adjusting a horizontal position for video display appliance are disclosed in U.S. Pat. No. 6,061,048 to Samsung Electronics Co., Ltd., entitled xe2x80x9cTechnique For Automatically Controlling The Centering Of monitor Screenxe2x80x9d, and U.S. Pat. No. 5,801,767 to Amtran Technology Co., Ltd., entitled xe2x80x9cImage Screen Automatic Adjustment for Video Monitorxe2x80x9d.
The above-described patents disclose features in common with the present invention but do not teach or suggest the specifically recited technique for automatically adjusting a horizontal position of the video display appliance as in the present invention.
FIG. 1 is a block diagram showing a conventional horizontal position adjustment circuit.
The conventional horizontal position adjustment circuit includes a front/back porch counter 120, a microprocessor 130 and a deflection circuit 140.
The front/back porch counter 120 receives a horizontal flyback pulse 110 and an RGB video signal 100 and outputs front porch and back porch signals.
The microprocessor 130 includes an I/O port for receiving the front-porch and the back-porch from the counter 120, and a processor for calculating and outputting a horizontal position value to place the display image in the center of the screen.
The deflection circuit 140 adjusts the horizontal position using the horizontal position value inputted from the microprocessor 130 to place the display image in the center of the screen.
FIG. 2 is a flowchart showing the firmware control procedure of the conventional horizontal position adjustment circuit. The conventional horizontal position adjustment circuit will be described in detail with reference to FIG. 2.
First, at step 200, if a new display mode is inputted or a user sets an automatic adjustment of a horizontal position, the front/back porch counter measures the front porch and the back porch using the horizontal flyback pulse and video signal and outputs the front porch and the back porch to the microprocessor at step 210.
Then, at step 220, the microprocessor calculates horizontal position data using the front porch and the back porch to place the position of the image in the center of the screen. At step 230, the calculated horizontal position data is outputted to the deflection circuit.
At step 240, the front/back porch counter measures again a new front porch and a new back porch, and checks whether or not the display image has been placed in the center of the screen.
If it is determined that the display image has not been placed in the center of the screen at step 250, the horizontal position data is calculated again using the front porch and back porch measured at step 260, and the procedure returns to step 230.
Meanwhile, if it is determined that the display image has been placed in the center of the screen at step 250, the procedure is ended.
However, the conventional horizontal position adjustment circuit has the disadvantage that it uses an expensive dedicated IC such as the front/back porch counter, and thus the circuitry becomes complicated with its cost increased.
It is therefore an object of the present invention to provide a horizontal position adjustment apparatus for a video display appliance that effectively makes adjustments of a horizontal position using simple and inexpensive circuits without the expensive front/back porch counter.
The present invention achieves the above-identified object by providing a horizontal position adjustment apparatus that comprises a comparative circuit, a horizontal position correction circuit and a deflection circuit.
The comparative circuit receives a horizontal flyback pulse and a video signal and outputs a first and second overlap signals.
The first and the second overlap signals are generated when the horizontal flyback signal is inputted with the video signal at the same time. And, the first overlap signal is generated in the left side of the total range of the available horizontal position and the second overlap signal is generating in the right side.
The horizontal position correction circuit receives the first and the second overlap signals from the comparative circuit, calculates a mean value of a first horizontal position value and a second position value and outputs the mean value as an adjustment value of the horizontal position. The first horizontal position value represents the horizontal position when the first overlap signal is generated and the second horizontal position value represents the horizontal position when the second overlap signal is generated.
The deflection circuit adjusts the horizontal position based on the adjustment value.
According to the above described feature of the present invention, the horizontal position may be adjusted using the overlap signal of the horizontal flyback pulse and the video signals to displace the display image into the center of the screen.
Furthermore, the present invention also provides a method of adjusting horizontal position of a video display appliance comprises the steps of detecting a first overlap signal representing that a horizontal flyback pulse is overlapped with a video signal in a left side of a total range of an available horizontal position; detecting a second overlap signal representing that the horizontal flyback pulse is overlapped with the video signal in a right side of the total range of the available horizontal position; calculating a mean value of a first horizontal position value and a second horizontal position value, the first horizontal position value corresponding to the horizontal position when the first overlap signal is generated, and the second horizontal position value corresponding to the horizontal position when the second overlap signal is generated; and adjusting the horizontal position based on the mean value that is used as an adjustment value of the horizontal position.